choosing spring rates

[Disturbed1]

just bought some nifty aragosta coilovers for my jza70 from japan which come with progressive spring rate of 12.3 front and 7.8 rears (or there abouts).

i will be putting these in my (fun track hack) circuit car im building up so was looking at buying some aftermarket linear Swift springs for them however not sure how to go about choosing the best rates/length springs.

the current fronts are 8" long while the rears are 10". the shocks have a max stroke of 3.5" back and front before bottoming out on bump stops.

now being a track dedicated supra, its significantly lighter then stock. about 1200 kilos with a weight distribution of approx 56/44. have access to corner weights so will get a better indication later.

have read up about theoretically calculaing wheel rates however most people in the know say its just trial and error. i dont have this kinda budget required for this option so would just like to get somethign close that i can live with and adapt drivign style to suit.

im only just getting into the sport so doubt i will be able to tell the diff no matter what i choose or based off the handling, that i would need softer rears or stiffer fronts etc etc....

if anyone has some ideas or knoledge or link to usefull info, would be great..

cheers

[Billzilla]

I'd start with 300 lb on the front and about 200lb on the rear. You might end up needing a bit more on the front though.

[Disturbed1]

what does that equate to in kg/m?

[takai]

I would say more than 300/200. More like 450/300lbs/in which is around 8 and 6kg.

[Billzilla]

what does that equate to in kg/m?

I don't know off the top of my head - no serious suspension place uses that way of measuring springs.

[charliechalk]

Instead of creating a new thread I thought I might post in here, being a generic title and all (If this is unacceptable let me know).

Currently in the boat of working out springs to purchase with a sleeve kit, car is an st162. I'm looking for something suitable for track use but not absolutely terrible on the road. I've been looking at similar weighted car set ups and the general consensus is 8-10kg/mm front (448-560lb/in) and 6-8kg/mm rear (336-448lb/in). Seen I've got practically no experience with how these will feel should I start at the soft end?

All suggestions are welcome, If we keep this neat I will try and make up a table with a guide to whatever models are mentioned and purposes

[abently]

Go down to the track you plan to race on when there's a track day and talk to the guys racing. Spring rates differ for each track, car corner or avg speed and suspension/tyre geometery to optomise grip & weight shift.

I'ld suggest probably just making a new thread if you can't find one specific to the st162 setup, but if you can get in contact with some CAMS logged st162 racers, then do that instead as they'll point you in the right direction.

[WDE_BDY]

what does that equate to in kg/m?

From kg/mm to lb/inch multiply by 56.
From lb/inch to kg/mm divide by 56.
Approximate number but close enough, should be 55.88.

Callum

[Disturbed1]

yeah saw a conversion chart but 300 lbs was only like 5.5 k which sounds way way to soft

[takai]

Its not, the Japs use stupidly heavy springs in their cars and then under dampen them. Its pretty well acknowleged however that under springing and over dampening is better.

I run 325lbs/in in the front of the Sprinter and 225lbs/in in the rear. Approximately what they ran for the GpA cars in the 80s.
For the A70 see if you can find out what they ran in GpA

[Disturbed1]

anyone know how to contact john smith?

[The Real Roadrunner]

Disturbed,

Id go around 650-800lbs in the front and about 250-300 in the back personally (it may need more but it depends on your valving etc.

The A70 runs a double A arm front and the coilovers bolt to about 2/3 of the way out to the wheel. you would need to do a few calcs to get the actual wheel rate but it is doable.

If its 1200kgs id want it fairly highly sprung but it does depend alot on valving (Jap = under damped)

cheers
Linden

[Disturbed1]

lets see if this means anythign to anyone haha

http://translate.google.com/translat...istory_state0=

cant read japanese so no idea what that plot is. these coilovers are made in netherlands/germany so have no idea of the valveing. they are 12 way damper adjustable and the difference between soft and hard is day and night, unlike my old teins which although felt different - not a great deal

[The Real Roadrunner]

Put them on a shock dyno to get a print out. easy

And compare them to the Teins on the same dyno so you know what your start point was


Cheers
Linden

[JustenGT8]

My Celica is ballpark 1400kg...56/44 weight split. I run (and this is effectively the wheel rate also) 550 front and 350 rear in a double progressive DMS spring. This is with TEIN HA dampners. I'm still playing with the TEIN rates but the spring rate feels pretty good.

Fact is you will have to start with something and see how it works, the chances of getting it spot on 1st go are pretty well nil...in fact the chances of you ever getting it spot on are nil given how much testing, data collection etc is needed by professional teams to do A simple change in tyres and rates will be way out again.

Get a base line with some cheaper springs that are theoretically close and go from there....no reason why you can't get it good enough.